Radiation generators, such as neutron and x-ray generators, are used in well logging tools to take measurements of a geological formation adjacent a wellbore where hydrocarbon resources may be located (e.g., oil and/or natural gas). Neutron generators may use deuterium-deuterium (d-d), deuterium-tritium (d-t) or tritium-tritium (t-t) reactions to create neutrons without the use of radioactive materials.
Radiation generators may include a tube (e.g., a neutron or x-ray tube) and associated electrical components, such as one or more high voltage transformers with a Cockcroft-Walton ladder to produce a high operating voltage. A neutron tube is a sealed envelope made of metal and insulators including a gas reservoir, an ion source, an accelerator column and a target. The target may be made of a hydride material. Once released from the reservoir, the gas is ionized in the ion source, and then accelerated in the accelerator column toward the target. A nuclear fusion reaction occurs between the incoming ions and the hydrogen isotope atoms present in the target, causing neutrons to be directed into the geological formation. A radiation detector may detect the radiation from the geological formation resulting from the neutron bombardment, which in turn provides information regarding the composition of the geological formation.
An x-ray tube has an electron source (often called an electron gun), an acceleration column and a target. The target may be made of a heavy material, such as tungsten or gold, for example.